The present invention relates to a color processing method and an apparatus therefor using two-dimensional (2-D) chromaticity separation, and more particularly, to a color processing method and apparatus for minimizing differences between a desired output color and the actual output color in a color display apparatus using 2-D chromaticity separation.
In general, a color display apparatus, specifically, a color television receiver receives and demodulates a color signal produced according to a broadcasting standard (NTSC or PAL) to then be reproduced via a CRT. However, the received color signal may be distorted for various reasons. One of the main reasons for such distortion is caused by the color signal processing in a color TV receiver. In particular, a color reproducibility difference between an input color and a CRT output color is generated due to the difference between R, G, B phosphor characteristics of a CRT and those of a predetermined broadcasting standard. Also, a color deviation of intermediate colors may be generated due to non-linearity of the color TV receiver circuit. Further, an output device such as a color TV receiver must complement insufficient portions of the original colors, or partially requires a visually-sensitive color processing due to the differences in subjective personal perferences for colors.
For solving such problems, a color correction apparatus for correcting a received color signal to suit a user's own taste in colors by adjusting two reference phases in a chromaticity demodulator of a color TV receiver, which is disclosed in U.S. Pat. No. 4,695,875, has been widely used. However, such apparatuses cause whole color distortion of residual colors other than the user's desired color.
As another conventional technology pertinent to classification of a color apparatus, there are several methods of modelling a relationship between an input color and an output color on the whole color space. Among them, typical methods are a matrixing method using regression analysis and a combined method using a look-up table and volume interpolation. Of the two, the latter method is for measuring multiple color values for obtaining an input-versus-output relationship of a system to then express intermediate values using these measuring points and volume interpolation. This method can obtain relatively exact results, compared to the conventional method. Also, since local color correction for the visually-sensitive color processing is possible, this method is widely used in color printing devices, which, however, is not suitable for commercial use since hardware implementation for real-time processing is difficult to achieve because of the complicated volume interpolation in a display apparatus such as a color TV receiver, and the apparatus adopting this method becomes undesirably expensive. Also, the matrixing method using regression analysis simply converts the input-versus-output relationship into matrices, based on multiple measuring points, which is widely used in a display field. However, the matrixing method must deal with the overall color space by a single matrix. Also, local color correction as in the visually-sensitive color adjustment is not allowed.
To solve such problems, there has been a recent proposal for a method pursuing a color apparatus classification by adopting regression analysis for each section by categorizing a color into five components: flesh, gray, red (R), green (G) and blue (B). However, by dividing the color into only five typical color components, boundaries may occur between the categorized sections. Also, it is difficult to properly exhibit characteristics of various colors expressed by color combination in the color apparatus. Further, local color correction is difficult to achieve in delicate color areas by the combined colors of five primary color components. The above-described problems also occur in another conventional method to locally correct using 6-separated hue region in chromaticity, as disclosed in U.S. Pat. No. 4,989,080.